A smart card generally comprises a single Integrated circuit, which is either a memory or a micro-controller. A smart card whose integrated circuit is a memory is commonly referred to as memory card. A smart card whose integrated circuit is a micro-controller is commonly referred to as microprocessor card.
A micro-controller typically comprises the following elements:                a central processing unit (CPU);        a volatile memory (RAM);        one of more non-volatile memories (ROM, EEPROM or Flash memory);        a communication interface for communication with a card excepting device, such as, for example, a mobile phone.        
The standards ISO 7816 and GSM11.11 relate to smart cards of the format ID-0 and ID-000, respectively.
The international patent application published under number WO200208487 describes a smart card comprising various integrated circuits. A communication bus couples the various integrated circuits which each other. The integrated circuits receive a supply voltage from a single power supply bus. There is thus a single supply voltage that is applied to each integrated circuit.
U.S. Pat. No. 5,490,117 discloses an IC card that comprises an integrated circuit that has an operating voltage of 3.3 V. The IC card can be used in a modem host system rated at 3.3 V or in a conventional host system rated at 5 V. The integrated circuit card comprises an analog switch, an external interface circuit, an internal interface circuits, and a high voltage detection circuit. If the voltage of the host system is less than or equal to an upper limit voltage of 4 V, the power supply voltage is applied unchanged through the analog switch to a ROM. On the other hand, if the power supply voltage is greater than this upper limit voltage of 4 V, the analog switch is made nonconductive and thus the power supply voltage is not applied to the ROM. This prevents the ROM from being destroyed. If a regulated-voltage circuit is also provided, a power supply voltage regulated at 3.3 V can be applied to the ROM, even when the power supply voltage of the host system is greater than the upper limit voltage of 4 V.